Introduction to fermentation biology

The ↓ production of biogas is based on a complex fermentation process by various microorganisms and requires a stable process environment.

In commercial plants, a number of factors might ↓ disrupt the balance of the fermentation biology and thus impair the production of biogas.

Download section

Biogas production

Typical problems in connection with fermenters

Interpreting the signs

Regular analysis

How to respond in the event of an emergency

Biogas production - a complex process

Biogas is the end product of an aerobic decomposition process. This process can be divided into four distinct phases. During each process step, various

microorganisms and a range of enzymes work symbiotically.

Biogas is produced in four phases

In a first step, known as the hydrolysis process, carbon hydrates are broken down into simple sugars, proteins into amino acids and fats into fatty acids. The products of the hydrolysis undergo an acidogenic process where organic acids and low alcohols are produced. The subsequent acetogenic process leads to the production of methane. The products of the acidogenic process are converted into acetic acid, carbon dioxide and hydrogen, which are the compounds required for the methanogenic process. If the process is well balanced, these phases are synchronised.

Conversion of fermentation substrate into biogas

Optimised nutrient supply ensures smooth processing

In order to ensure that the above processes are completed properly, stable process conditions must be established. The supply of nutrients and essential trace elements to the microorganisms involved in the processes is thereby a key factor.

Trace elements are vital for the production of cellular material,

and in particular for the production of enzymes and coenzymes, which in turn act as versatile catalysts for individual reactions in the processes described above. The production of methane from CO₂ and H₂ for example involves seven different enzymes and three coenzymes.

Just the right amount – the nutrient balance is of great importance

The fermentation process is governed by the Liebig's "Law of the Minimum". It states that, if there is a deficiency of only one nutrient, it is not possible to achieve potential yield, as this nutrient is the limiting factor. On the other hand, it has been shown that excess availability of minerals can have a toxic effect on microorganisms.

As for some elements, the optimum supply and toxic quantities are however very close to each other, accurate analysis and precision dosing of the trace elements is required to achieve optimised methane production. From the point of view of soil protection, excess concentrations of micro and macro-nutrients should be avoided in order to prevent damage to the environment.

Biogas production - a complex process

The development of an organism is determined by the most scarce resource

Practical study: If the fermentation biology is out of balance

Typical problems in the fermentation biology

A deficiency of essential nutrients is not the only cause for impaired fermentation. There are other "typical" operating errors such as sudden changes in the fermenter temperature, excess nutrient supply upon substrate change or the fast feed of substrates with high fat or protein content.

Click here for a list of typical problems, their causes and possible remedies

Detecting problems at an early stage

Not all process disruptions can be easily identified. Some fermenter problems develop slowly over a long time. There might be several months before the consequences of an event become apparent. Operators therefore must heed even minor changes in the process and identify their causes.

List of typical signs of slowly developing problems

Regular analysis for the early detection of problems

In order to detect disruptions in the process at the earliest possible stage, we recommend that operators carry out regular fermenter analyses. This applies in particular to plants with high throughput rates or where a number of different substrates are processed.

Some analyses can be carried out by the operator. For others, samples must be examined in a lab.

List of useful analyses

What to do when things go wrong

Despite all precautions, fermentation processes can go wrong. Serious problems are often due to a number of causes that are interlinked.

Never just wait and hope that the fermenter will regain its balance again. You must identify the cause of the problem and develop a plan to rectify the situation and to prevent it in the future.

Emergency checklist